The purpose of this study is to define the metastatic suppressor role of KAI1 in prostate cancer (CaP). We hypothesize that: (Specific aim 1) KAI1 is a predictive molecular marker of metastasis and therefore a prognostic indicator in prostate cancer patients; (2) KAI1 is downregulated in prostatic intraepithelial neoplasia (PIN), the purported precursor to CaP; (3) KAI1 is involved in the transition of androgen-dependent to androgen-independent CaP; and (4) KAI1 exerts its suppressive activity at several points during the metastatic cascade.